Production of thermally hardenable boron-titanium steels



Patented Nov. 7, 1950 UNITED STATES PATENT OFFICE PRODUCTION OF THERMALLY HARDENABLE BORON-TITANIUM STEELS Maurice J. Day, Oak Park, Ill., assignor to Carnegie-Illinois Steel Corporation, a corporation of New Jersey No Drawing. Application June 28, 1948, Serial No. 35,733

2 times the amount which the nitrogen exceeds .006% or 5 .01e%.

The efiiciency of such additions can be readily seen from the following tabulation based on steels having otherwise similar composition, except for boron and titanium. The hardenability factor clearly shows the effectiveness of the titanium.

EXAMPLE I Steel Ahigh nitrogen Mn P S Ni Cr M0 V B N Ti 1. 92 77 .30 ()3 0024 011 None due to its greater effectiveness therein but may be and frequently is added to steels containing up to .90% carbon. However, even in the case of the low carbon steels, the effect of the boron additions varies widely, i. e., boron additions will Hardenability for boron calculated to be 1.04 Where 1.00 is equivalent to no effect of boron.

EXAMPLE II Steel B-high nitrogen '0 Mn P S Ni Cr Mo V -B N Ti remarkably increase the hardenability of one steel and have little or no effect on steels of generally similar composition.

It is accordingly an object of this invention to provide a uniform increase in hardenability by boron additions to thermally hardenable steels.

It is a further object to obtain maximum eniciency from boron additions to thermally hardenable steels.

It has heretofore been noted by a number of metallurgists that boron additions to steels produced in open hearth furnaces provide the desired increase in hardenability. However, boron additions make little, if any, change in this property of steels produced in electric furnaces. I have discovered that this difference in response to boron is due to the nitrogen content and that steels containing no more than .006% nitrogen will respond effectively to boron additions. I have further discovered that steels containing over .006% nitrogen may be rendered very responsive to improvement in hardenability by boron additions by adding at least .02% titanium to the molten steel prior to or simultaneously With the boron. In electric furnace steels, the nitrogen content may use as high as .02% or higher. To obtain the maximum efficiency from the titanium and boron additions to steel containing large amounts of nitrogen, the titanium should be added in amounts at least five times the amount the nitrogen content exceeds .006%. Thus for a steel containing .02% nitrogen about .07% titanium should be added, which is five Hardenability factor for boron calculated to be 1.71 which is a satisfactory performance for boron.

I claim:

The method of improving the efficiency of boron additions to thermally hardenable steels containing over .006% nitrogen comprising adding at least .02% titanium to the molten steel prior to adding the boron, the titanium addition being at least five times the amount the nitrogen content exceeds .006%.

MAURICE J. DAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Crafts Apr. 21, 1942 OTHER REFERENCES Number 

